Abstract:

Background: Contaminated water bodies like rivers harboring extended-spectrum beta-lactamase and carbapenem-resistant gram-negative bacteria (ESBL-GNB and CR-GNB) is a major public health concern. They pose a risk of transmission to humans through recreational activities or domestic consumptions. Limited data available regarding river contaminations by ESBL-PE and CR-GNB especially in low- and middle-income countries (LMICs) like Tanzania. Hence, the study which aims to determine rate of contamination by ESBL-PE and CR-GNB in River Mirongo water, to promote public health and environmental safety in Mwanza, Tanzania.

Methods: This cross-sectional environmental-based study, was conducted in River Mirongo between June and August 2024 in Mwanza, Tanzania. Checklist was used for data collection while sterile specimen containers was used for collection of muddy-water from River Mirongo. Samples was sent to CUHAS Microbiology research laboratory for processing. Samples were directly inoculated on MacConkey agar supplemented with cefotaxime 2µg/ml (MCA-C) for isolation of beta-lactamase producing gram-negative bacteria quantitatively expressed by colony forming unit of bacteria per milliliters of water sample. Disk combination test was used for phenotypic detection of ESBL-PE and CR-GNB. STATA version 15.0 was used for data analysis.

Results: A total of 160 3rd generation cephalosporin-resistant gram-negative bacteria (3GC-R-GNB) isolates were recovered from 240 samples in which 54.16% (130/240) were ESBL-PE phenotypes, K. pneumoniae (31.72%) and E. coli (28.97%) formed the majority of ESBL isolates whereas 4.16% (10/240) were CR phenotypes, unidentified gram-negative rods (GNR) (40%) and E. cloacae (30%) formed majority of the CR isolates. Heavy growth of 3GC-R-GNB was observed in day 1 in week 2, day 2 in week 3, day 1 in week 4 and day 2 in week 5 and both days in week 7 in which majority of growth were observed in sites with domestic waste dumping, hospital, agricultural and livestock activities.

Conclusion: This study reported a prevalence of 54.16% and 4.16% of collected river water samples by ESBL-PE and CR-GNB respectively in which K. pneumoniae, E. coli and E. cloacae were predominant organisms, sampling sites with positive growth for ESBL-PE and CR-GNB included domestic waste dumping, hospital, agriculture and livestock keeping. And high positive growth was observed varying with a duration of time due to rain and overflow of river in days with peaks of positives.